illustris

This page is inspired by scientific work which is by no means pulp fiction. Instead, recent articles are dealing with one of the still unsolved questions in physics: the understanding of what we colloquially refer to as 'juice' when we charge our smartphones or electric cars. The word ‘fiction’ in the name was deliberately chosen in a positive sense. In contrast to examples on the science delusion page, which deals with the misuse of science to achieve political goals, physicists in this field strive for knowledge. They devise hypotheses (fiction in a sense), create mathematical models, and conduct experiments to validate or falsify them in order to describe the nature of electrical charge conduction in such a way that all experimental observations can be explained coherently.

What? you may ask, electrons conduct electricity! This has been known since the 19th century, when George J. Stoney and Hermann von Helmholtz coined the term for the smallest, indivisible amount of electric charge. But it's not that simple, at least not since 1986, the year Georg Bednorz and Karl Alexander Müller discovered superconductivity in ceramic materials.

Superconductivity may play a crucial part of future economies relying to large extents on electricity. This is another, complementary aspect of this page because electricity is discussed on the page science delusion as solution for fossil free economies. Below, a short introduction of the classic physical models for conductivity in 'normal' metals is given. It precedes a brief summary of the current understanding of conduction in 'strange' metals, formulated in a simplified way by a non physicist. Finally, artistic impressions are shown for imagination … not least of science fiction becoming true.

The above description of electrical conductivity by electrons does not reflect contradictory aspects such as the electrical repulsion of particles with the same charge. Furthermore, elementary particles cannot be described using classical physics, but rather quantum mechanics. Electrons have a half-integer spin and thus obey Fermi-Dirac statistics and Pauli's exclusion principle: no quantum state can be occupied by more than one fermion with the same quantum numbers. The charge carriers in a metal can thus be regarded as a Fermi gas consisting of non-interacting electrons, similar to a classical ideal gas.

This also calls into question the classical interpretation of electrical resistance in metals, namely the scattering of electrons at the metal ions (Drude model). According to this model, the mean free path of the electrons should correspond approximately to the lattice spacing in the crystal. Experimental relaxation times, however, yield a mean free path in the range of a few hundred Ångstroms. This is plausible, since the positive charge of the metal ions is shielded by the many electrons that are still 'locked in' by the ions. Furthermore, this much larger free path length is in the range of omnipresent defects in solid materials (lattice defects, impurities) or of thermal fluctuations. A note at this point: this refers to technical grade materials, not laboratory samples made from ultra-pure chemistry under meticulously controlled conditions on tiny length scales. In practice − besides impurities and lattice defects − crystalline solids obtained from melts are polycrystalline and on larger scales (from μm to mm) grains are composing metals.

On the contrary, electrons in an ideal Fermi gas − owing to their quantum mechanic nature − would have 'infinite' mean free paths, limited only by the macroscopic size of the conductor which is unreasonable. Therefore some unknown interactions are causing the electrons to condense into a Fermi liquid. Based on the theory of phase transitions developed by Lev Landau in the 1950s, the Ginzburg-Landau theory describes electrical conductivity as the result of quasiparticles consisting of electrons. These clumped electrons are thought to form a ‘superfluid’ when the metal transitions to the superconducting state.

A microscopic picture was postulated in 1957 by John Boarden, Leon Cooper, and John Robert Schieffer (BCS theory). They suggested that two conduction electrons are forming a pair, known as Cooper pair. Mechanistically, they speculated that electrons may distort the ion lattice at low temperatures through electrostatic attraction which in turn would enable attractive force between the electrons themselves. As quasiparticles, such pairs have an integer spin (½ + ½) and thus behave like bosons, which are 'allowed' to condense and migrate through the ion lattice in their lowest possible energy state without scattering. Inelastic collisions at the ion lattice would lead to the dissociation of the Cooper pairs and the transition to a higher (unfavourable) energetic state.

The BCS theory fails to explain superconductivity at higher temperatures where the energy gain from lattice distortion and quasiparticle condensation is overcome by the thermal energy of the oscillating ions. Nevertheless, in 1986 Georg Bednorz and Karl Alexander Müller discovered high-temperature (Tc > 35 K) superconductivity in the IBM laboratory in Zürich. Although the superconducting materials like bismuth strontium calcium copper oxide (BSCCO, Tc 107 K) were ceramics (cuprates), these are nowadays also called 'strange metals'. Strange because of their peculiar temperature-conductivity relation above the critical temperature: the linear resistivity increase (purple curve in the figure above) is proportional to the Planck constant and it doesn't level off at higher temperatures as it is found with normal metals (that T-regime is not shown in the figure above). Despite being superconductors, some strange metals are rather poor conductors at high temperatures in comparison to 'normal' metals. Until nowadays (2025) researchers are still wondering what might be glueing the electrons to enable superconductivity at high* temperatures, supposed that it's also working according to the BCS theory. Furthermore, an explanation for the linear temperature dependency above Tc is missing. This 'Planckian dissipation' was found to be a common feature of all cuprates not before 2019.

*: 'high temperature' in relation to the 'low temperature' for superconductivity in 'normal' metals

Going beyond quasiparticles, it was assumed that this strange electron behavior is reflecting fundamentally new physics. Theoretical physicist Jan Zaanen from Leiden University summarized ideas about that nature of conductivity in 2019 which drew broader attention to that phenomenon. Several groups are trying to find explanations, theoretically [1] and by performing experiments, in particular shot noise measurements [2], terahertz time-domain transmission spectroscopy [3], diffuse X-ray scattering [4] as well as the interaction with beams of neutrons and of electrons. Without going into details, the experimental results and theoretical considerations are pointing to coexistent populations of entangled electrons (conducting ones and those locked by the ions) rather than quasiparticles. Some physicists are even thinking about 'unparticles', a hypothetical kind of matter whose mass can take any value depending on how it's been measured. In any case, the superconducting state of strange metals seems to be distinctly void of noise which is a sign of homogeneous flow (cf. figure below)*. Some researcher in the field are speaking about a quantum-entangled soup of electrons (n.b.: isn't it a Fermi liquid?) while other prefer the image of frustrated charge carriers which just reorganize at lower temperature for superconductivity. Philip W. Phillips (University of Illinois) is thinking beyond electrons for electricity in general [5].

*: It should be noted that the absence of noise could only be proven at low temperatures, not near the high Tc of the strange metal

However, all researcher in the field are hoping that a comprehensive understanding of strange metal conductivity will help to find materials that are superconducting at ambient conditions or at even higher temperatures. This would heave the world's energy supply on a higher level.